The science of sports has in recent decades expanded to assist athletes with knowledge, guidance and training in numerous areas; including but not limited to nutrition, physical fitness, aerodynamics, muscle development, sports psychology and more.
In sports like baseball, golf and tennis, the subject of swing dynamics is heavily researched with the result that athletes are being educated more and more how to position and rotate their bodies to impart the greatest amount of force as well as swing speed to swing a club or bat to hit a ball farther and farther. Along with body position, swing exercises are taught young athletes to develop good swing characteristics as early as possible.
In addition, training aids have become popular in order to position arm and shoulder movement and to strengthen the arms, hands and wrists. For example, the MEDICUS® golf club is a training aid which has a break-away in the shaft near the club head. That break-away is designed to break when the swing arc is out of the desired swing arc area with the misdirected force causing the club to “fold.” When the swing characteristics are correct, the club remains configured as a typical club, and allows the user to swing through to hit a golf ball without the breaking down of the club.
In another example, the recent marketing of the shaker weight for women shows a dumbbell shaped weight with an inner portion of the weight movable along the axis of the weight handle, captured therein, providing a reciprocating or dynamic component to the action of the weight, further challenging not only the traditional muscles exercised by a simple dumbbell, but other associated muscles which are affected by the dynamic motion.
In the sport of baseball, many tests have shown that rotational mechanics are far more efficient than linear mechanics in developing bat speed. In order to understand why this is true, it is important to understand the forces acting on the bat.
Other than the effects of gravity, drag and other minor factors, there are two forces acting on the bat that create bat speed; Circular Hand Path (CHP)—The transfer of the body's rotational momentum that occurs when the hands are taken in a circular path; and Torque—Torque is applied at the handle of the bat by the push/pull of the hands/arms/shoulders.
In considering Circular Hand Path, the bat will undergo angular displacement (i.e., bat speed) when the path of the hands is also undergoing angular displacement (i.e., a circular hand path). In other words, as long as the path of the hands stays in a circular path as the body rotates, the circular hand path will transfer the body's rotational momentum into bat-head acceleration.
CHP is often referred to as the “Pendulum Effect” so as to distinguish it from the “Crack of the Whip” theory. A pendulum is simply an object that swings freely back and forth in a circular arc. But, in the baseball swing, there are two pendulums at work at the same time: 1) the lead-arm swings the hands in a circular arc, and 2) the end of the bat swings around the hands. This is referred to as the Double Pendulum Effect of a CHP. A double pendulum consists of one pendulum attached to another.
Linear mechanics is much different in that it does not rely on a circular arc or Pendulum Effect, as it is based on a theory that when the hands are extended in a straight line, the bat-head will suddenly accelerate to contact like the crack of a whip (“Crack of the Whip theory”.) However, this theory is flawed since there is no whip effect in the baseball swing (a bat is not flexible like a whip), and consequently, efforts to produce a whip effect have stalled many hitters progress for decades. This is far different from the sport of golf, where the golf club shaft varies in degrees of stiffness, depending on the ability of the golfer to generate clubhead speed. The higher the clubhead speed, the stiffer the golf club shaft employed.
A substantial portion of a good hitter's bat speed is derived from the circular path of his hands (think of swinging a weight on the end of a string). As long as the hands are maintained in a circular path, the weight will continue to accelerate in a circle. However, if the path of the hand straightens, the weight on the end of the string loses angular velocity and trails behind the hands.
The same rational applies when a hitter is swinging a bat. If the hands are kept in a circular path, the bat will continue to accelerate. But if the hands straighten, the batter loses the circular path and the bat will lose speed. With a straighter hand path, the bat-head trails behind the hands well into the swing. This is often referred to as “knob of the bat first” and results in poor bat speed.
In considering the effect of Torque specifically upon the swing, Torque is the result of two forces being applied to an object from opposing directions that cause the object to rotate about a point. Forces in the same direction may cause the object to accelerate, but will not cause the object to rotate about a point (which therefore means no angular displacement). For example, when loosening a lug nut with a 4-prong tire wrench, you push down with one hand while pulling up with the other (torque). However, if you push down (or pull up) with both hands, you would not cause the nut to rotate; i.e., no torque results.
Torque is applied in the swing by the concurrent push and pull action of the forearms and hands. The bat head is accelerated from torque when the direction of force applied by the hands is from opposing directions.
To reach maximum bat speed, the batter must apply torque from initiation to contact and keep the hands in a circular path.
Average hitters usually have little circular hand path in their swing (no pendulum effect) due to the straighter hand path. As a result, average hitters rely mainly on torque to accelerate the bat hitting area.
For a batter to attain his maximum potential, his mechanics must make efficient use of both CHP and Torque. Great hitters generate high bat speed because their swing mechanics efficiently apply torque at the handle that compliments their circular hand path.
Most batting instructors would agree that there is a correlation between the velocity of the bat and how far a hit ball will travel. But, two players swinging the same bat on about the same plane with comparable bat speeds may vary greatly in the power they display. One might hit balls significantly farther than the other. This would seem to be contradictory unless one takes into account when the maximum bat speed occurred during the two swings.
The bat speed that really counts is that attained at impact with the ball. Swing mechanics of a great hitter allows the generation of higher bat speed much earlier in the swing compared with average hitters. Players with a lot of “pop” in their bat expend all the body's rotational and torque energies before and at impact. After impact, the batter's limbs and torso reach a relaxed and coast mode. The follow through portion of the swing is from the momentum of the bat pulling the arms up and through
Some hitters continue to expend energy to gain bat speed for anywhere from 20 to 40 degrees (average hitters) to as much as 60 degrees and beyond (poor hitters) of bat travel after the bat passes the contact point. Some coaches would contend that gaining speed after contact is beneficial because of the “driving through the ball” effect. The facts do not support this theory. The ball is in contact with a 35 oz. wood bat moving at perhaps 70 MPH for about 1/2000 of a second. During this time the bat moves less than 1 in. (about ¾ in.) This phenomenon does not provide much opportunity for “driving through” the ball.
Wrists play an important role in producing power and quickness for both the baseball and golf swings. But the muscle groups that flex and un-flex (abduct and adduct) the wrist are a relatively small muscle group and have a limited impact on the generation of bat speed.
For a ball to be hit over 400 feet, the bat head must be accelerated to a speed in excess of 70 MPH in less than 5/30 of a second. About half that speed is developed in the last 1/30 of a second. The large amount of inertia that must be overcome to accelerate the bat head 35 MPH or more in 1/30 of a second requires far more energy than the muscles in the hands, wrists and arms can produce. That kind of energy (about 3 torque HP) must come from the large muscle groups in the legs, back and shoulders.
The question then becomes; how is the energy transferred from the large muscle groups of the body up and on out to the bat head? The large muscles in the legs and back must rotate the hips and shoulders to a point where the abdomen and chest face the pitcher. The lead shoulder must rotate back in the direction of the catcher. This means that the lead arm, and thus the bottom hand, are now being pulling back toward the catcher as the bat approaches contact at the same time the rear shoulder and top hand are rotating around toward the pitcher.
This generates a tremendous amount of TORQUE on the bat. As stated, Torque is the result of forces being applied to the bat from opposing directions that causes it to rotate about a point between the hands.
So, in the swing of a great hitter, what appears to be wrist action is actually the “push-pull” action of the hands generating a large amount of torque. This torque was developed from the large muscle groups and causes the bat head to be greatly accelerated.—If the batter does not initiate the swing with torque and rotational forces, he will not be able to obtain the position of power required to apply maximum torque to the bat before contact. This is especially true for pitches on the outside part of the plate.
Consequently, it is important for the batter to not only develop the large muscle groups to allow the appropriate rotation of the body during the swing, but to also develop the arms and wrists to generate the circular motion required to maximize the torque which can be applied by the push and pull of the hands, thereby having the hands move in a circular motion relative to the end of the bat as well as to crack the whip and produce the maximum pop of the swing.
Just swinging the bat repetitiously does have an effect on the strengthening of the muscles, but sometimes, too much repetition can also fatigue the player. In addition, it is simply not practical to strengthen the wrists, forearms and torso by swinging a bat when in a gymnasium setting or at home or in crowded areas or confined spaces.
What is needed is a focused training aid which can be used by an athlete hoping to strengthen the necessary wrist, forearm and shoulder muscles without the need to swing a 35 oz. bat about when doing so might be dangerous.
Furthermore, simply swinging the bat does not necessarily focus the strengthening of the wrist muscles, or provide the torque challenge to the athlete in and of itself. What is needed then is a training aid which applies forces to the user which naturally strengthen the wrist, forearm and shoulder muscles, keying on the muscles necessary to improve the torque of the swing by the ability to more easily rotate the hands in a circular motion at the same time the bat is swung.